The present invention relates generally to pure fluid systems, and more particularly, to a fluidic complementary gain changing circuit.
In the past, gain changing for fluid amplifiers has been achieved using various techniques. One of these involves selective switching among several fluid amplifiers, each having a different gain from the others, according to the specific gain desired for a given application. Another technique requires the selective addition of fluid through a port to an interaction chamber of the fluid amplifier, to vary the gain. Other known techniques include use of a fluidic amplifier cascade, variable area resistor, and fluidic operational amplifier with variable input resistor. Each of these gain changers is of the single push-pull type.
Still another technique, described in U.S. Pat. No. 3,499,460, issued Mar. 10, 1970, to Rainer, involves the use of a pair of identical general purpose proportional fluid amplifiers in a fluidic circuit whose gain is changed by varying the magnitude of a bias pressure common to both amplifiers. A differential pressure signal is produced between output channels of the two amplifiers. If the pressures of the input fluid streams to the amplifiers are equal, and the amplifiers are biased by equal pressures at their respective control ports, the differential output signal between outlet channels of the two amplifiers is zero. A change in the bias pressure at the control ports of the two amplifiers produces a change in the overall circuit's differential output signal, and thus may be used to vary the fluidic circuit gain. Accordingly, the differential pressure (input signal) applied to the control ports of a third proportional fluid amplifier that supplies differential output pressures as input supply pressures to the other two amplifiers, is amplified or not according to the selected gain of the overall circuit.
For some applications, it is desirable to provide a complementary gain changing function in a fluidic circuit, which is not achievable using any of the aforementioned techniques. In particular, the capability to provide simultaneous dual outputs of high and low gain is a desirable feature for the fluidic flight control systems of certain aircraft, such as a vertical/standard take-off and landing (V/STOL) aircraft.
Accordingly, it is a principal object of the present invention to provide a pure fluidic complementary gain changing circuit.
Another general object of the invention is to provide a fluidic complementary gain changer in which the fluidic circuit gain is selectively adjustable such that complementary outputs are derived from opposite gain extremes ranging upward to approximately one hundred percent versus a concurrent zero percent.